ω-Heteroaroyl(propionyl or butyryl)-L-prolines

ABSTRACT

This disclosure describes novel substituted  omega -heteroaroyl(propionyl or butyryl)-L-prolines and the esters and cationic salts thereof which are useful as hypotensive agents in mammals.

BRIEF SUMMARY OF THE INVENTION

This invention relates to new organic compounds and, more particularly,is concerned with novel ω-heteroaroyl(propionyl or butyryl)-L-prolinesand esters thereof which may be represented by the following generalformulae: ##STR1## wherein R₁ is hydrogen or alkyl having from 1-3carbon atoms; R₂ is hydrogen or alkyl having from 1-3 carbon atoms; R₃is mercapto, formylthio, benzoylthio, alkanoylthio having from 2-4carbon atoms or moieties of the formulae: ##STR2## R₄ is hydrogen oralkyl having from 1-4 carbon atoms; R₅ is hydrogen or alkyl having from1-4 carbon atoms; and heteroaryl is selected from the group consistingof moieties of the formula: ##STR3## wherein R₇ is hydrogen, fluoro,chloro, bromo or alkyl having from 1-4 carbon atoms and R₉ is hydrogenor alkyl having from 1-4 carbon atoms; and the pharmacologicallyacceptable cationic salts thereof when R₅ is hydrogen.

The novel compounds of the present invention possess asymmetric carbonatoms (which are indicated by asterisks) and thus exist indiastereoisomeric forms.

DETAILED DESCRIPTION OF THE INVENTION

The novel ω-heteroaroyl(propionyl or butyryl)-L-prolines and estersthereof of the present invention are generally obtainable as white toyellow solids having characteristic absorption spectra or are obtainedas white or yellow crystals with characteristic melting points andabsorption spectra. They are generally soluble in many organic solventssuch as lower alkanols, tetrahydrofuran, dioxane, chloroform and thelike.

Also included within the purview of the present invention are thecationic salts of the compounds of the above general formulae wherein R₅is hydrogen. The useful pharmaceutically acceptable salts of thecompounds wherein R₅ is hydrogen are those with pharmacologicallyacceptable metal cations, ammonium, amine cations, or quaternaryammonium cations. Preferred metal cations are those derived from thealkali metals, e.g. lithium, sodium and potassium, and from the alkalineearth metals, e.g. magnesium and calcium, although cationic forms ofother metals, e.g. aluminum, copper, iron and in particular zinc, arewithin the scope of the invention. Pharmacologically acceptable aminecations are those derived from primary, secondary or tertiary aminessuch as mono-, di- or trimethylamine, ethylamine, dibutylamine,triisopropylamine, N-methylhexylamine, decylamine, allylamine,cyclopentylamine, dicyclohexylamine, mono- or dibenzylamine, α- orβ-phenylethylamine, ethylenediamine, and arylaliphatic amines containingup to and including 18 carbon atoms, as well as heterocyclic amines,e.g. piperidine, morpholine, pyrrolidine, piperazine and lower alkylderivatives thereof, e.g. 1-methylpiperidine, 4-ethylmorpholine,1-isopropylpyrrolidine, 1,4-dimethylpiperazine, and the like, as well asamines containing water-solubilizing or hydrophilic groups, e.g. mono-,di-, or triethanolamine, N-butylethanolamine, 2-amino- 1-butanol,2-amino-2-ethyl-1,3-propanediol, tris(hydroxymethyl)aminomethane,N-phenylethanolamine, galactamine, N-methylglucosamine, ephedrine,phenylephrine, epinephrine, procaine, and the like. Examples of suitablepharmacologically acceptable quaternary ammonium cations aretetramethylammonium, tetraethylammonium, benzyltrimethylammonium,phenyltriethylammonium, and the like.

Angiotensin II is a powerful vasoconstrictor agent that has beenimplicated as the main causative agent in the etiology of renovascularhypertension. Angiotensin II is formed from angiotensin I by the actionof angiotensin converting enzyme. Angiotensin I is a biologically inertdecapeptide cleaved from the blood protein angiotensinogen by the actionof the enzyme renin [Oparil et al., New England J. of Med., 291, 389-457(1974)]. Angiotensinogen and renin are also biologically inert. Agentsthat inhibit angiotens in converting enzyme can therefore counteract thepressor efect of angiotensin I since this is due only to its conversionto angiotensin II. These agents can be used therapeutically in thetreatment of forms of renovascular and malignant hypertension as well asother forms of angiotensin dependent hypertension [Gavras, et al., NewEngland J. of Med. 291, 817 (1974)].

The novel compounds of this invention inhibit angiotensin convertingenzyme and thus inhibit the conversion of angiotensin I to angiotensinII and are therefore useful in reducing hypertension, especiallyangiotensin related hypertension in various mammalian species. Theactivity of the novel compounds of this invention as hypotensive agentswas established in two systems which measure their ability asangiotensin converting enzyme inhibitors; by utilizing aspectrophotometric assay of the compounds in vitro and by themeasurement of the blood pressure lowering effect of the compounds inthe aorta-coarcted renal hypertensive rats.

Spectrophotometric Assay for Angiotensin Converting Enzyme Inhibitors

The in vitro activity for inhibition of the angiotensin convertingenzyme (ACE) was measured by the method of Cushman, D. W. and Cheung, H.S., Biochem. Pharmacol., 20, 1637-1648 (1971), usingbenzoyl-glycyl-histidyl-leucine as the substrate. The reaction mixtureconsisted of 50 μl. of potassium phosphate (500 mM., pH 10.2), 30 ml. ofsodium chloride (2500 mM.), 25 μl. of substrate (50 mM), 30 to 50 μl. ofthe crude extract of ACE, 10 μl. of test compound (2.5 mM.) or vehicleand a suitable amount of distilled water to give a total volume of 250μl. This reaction mixture was incubated for 30 minutes at 37° C. and thereaction was then terminated by the addition of 250 μl. of 1Nhydrochloric acid. The hippuric acid was then extracted with 1.5 ml. ofethyl acetate by vortex mixing for 15 seconds. After centrifugation, oneml. of th ethyl acetate layer was pipetted into a new tube and vaporatedto dryness. The extracted hippuric acid was then dissolved in one ml. ofwater and the amount of this acid was then measured by its absorbance at228 nm. The ACE was extracted from rabbit lung acetone powder (Pel-FreezBiol. Inc.) by blending 5 g. of the powder in 50 ml. of phosphate buffer(50 mM., pH 8.3) and then centrifuging at 40,000 g for 40 minutes. Thesupernatant was then kept at 5° C. and used as the enzyme source. Theactivity of the ACE inhibitor was calculated as the percent inhibitionof ACE activity compared to the control value of that particular assay.A full dose-response inhibitory curve is then performed to determine theIC₅₀ value which may be defined as the molar concentration of a compoundthat will inhibit the ACE activity by 50%. Representative compounds ofthe present invention and their corresponding IC₅₀ values as determinedby the above procedure are set forth in Table I below.

                  TABLE I                                                         ______________________________________                                        Angiotensin Converting Enzyme Inhibitors                                       Compound           IC.sub.50 (10.sup.-7 M)                                   ______________________________________                                        1-[3-(Acetylthio)-3-(2-thenoyl)-                                                                  2.56                                                      propionyl]-L-proline                                                          1-[3-(Acetylthio)-3-(5-bromo-2-                                                                   1.09                                                      thenoyl)propionyl]-L-proline                                                  1-[3-(Acetylthio)-3-(5-chloro-2-                                                                  1.08                                                      thenoyl)propionyl]-L-proline                                                  1-[3-(Acetylthio)-3-(benzo[b]-                                                                    1.39                                                      thien-3-ylcarbonyl)propionyl]-L-                                              proline                                                                       1-[3-(Acetylthio)-3-(2-furoyl)-                                                                   6.75                                                      propionyl-L-proline                                                           1-[3-(Acetylthio)-3-(2-benzofur-                                                                  0.74                                                      anylcarbonyl)propionyl]-L-                                                    proline                                                                       1-[3-(Acetylthio)-3-(benzo[b]-                                                                    210                                                       thien-2-ylcarbonyl)-2-methyl-                                                 propionyl]-L-proline                                                          ______________________________________                                    

Measurement of Arterial Blood Pressure in Aorta-Coarcted RenalHypertensive Rats

Male, Sprague-Dawley normotensive rats, weighing 300-325 g. (CharlesRiver Breeding Lab. Inc., Wilmington, Mass.) were maintained on PurinaLaboratory Chow and tap water ad libitum for 1-7 days before use.Hypertension was induced by complete ligation of the aorta between theorigin of the renal arteries, according to the method of Rojo-Ortega,J.M. and Genest, J., A Method for Production of ExperimentalHypertension in Rats, in Can. J. Physiol. Pharmacol. 46, 883-885 (1968),with modifications of the surgical procedures. Thus, rats wereanesthetized with methohexitol sodium at 66 mg./kg. of body weight,intraperitoneally and were laid on their right side. An incision wasmade just below the rib cage on their left side. With a cotton-tip swab,the fat was gently pushed back to expose the left kidney. The kidney washeld gently between the thumb and the forefinger outside of the bodycavity. The aorta was completely ligated between the origin of the renalarteries with a No. -000 silk suture. Care was taken to avoid theocclusion of the mesenteric artery. The wound was then closed in twolayers using a 4-0 polyglycolic acid suture on the muscle and woundclips on the skin. The wound is then sprayed with No. 3 thimerosalaerosol. Following this surgery, the rats were returned to their cagesand provided with Purina Laboratory Chow and water ad libitum. Six daysafter surgery, the conscious rats were restrained on rat boards withelastic tape. The neck area was locally anesthetized by subcutaneousinfiltration of 2% lidocaine. After the trachea was cannulated and therat respired spontaneously, the carotid artery was isolated andcannulated with a nylon catheter (inside diameter -0.015", outsidediameter 0.030") which was connected to a Statham P23Gb pressuretransducer--Gold Brush recorder (Model 2400) for monitoring bloodpressure. The test comounds were dissolved in a small amount of ethanoland then diluted to the desired concentration with saline. Both thesolution of the test compound and the vehicle alone were administeredorally and run parallel in each experiment. The following representativecompounds of the present invention were considered active when tested bythis procedure:

1-[3-(Acetylthio)-3-(2-thenoyl)propionyl]-L-proline

1-[3-(Acetylthio)-3-(5-bromo-2-thenoyl)-propionyl]-L-proline

1-[3-(Acetylthio)-3-(5-bromo-2-thenoyl)-propionyl]-L-proline

1-[3-(Acetylthio)-3-(benzo[b]thien-3-yl-carbonyl)propionyl]-L-proline

1-[3-(Acetylthio)-3-(2-furoyl)propionyl]-L-proline.

The novel compounds of the present invention have thus been found to behighly useful for lowering elevated blood pressure in mammals whenadministered in amounts ranging from about one mg. to about 1000 mg. perkilogram of body weight per day. A preferred dosage regimen for optimumresults would be from about 10 mg. to about 300 mg. per kilogram of bodyweight per day. The dosage regimen may be adjusted to provide theoptimum therapeutic response. For example, several divided doses may beadministered daily or the dose may be proportionally reduced asindicated by the exigencies of the therapeutic situation. The activecompounds are preferrably administered orally but may be administered inany convenient manner such as by the intravenous, intramuscular orsubcutaneous routes.

Compositions according to the present invention having the desiredclarity, stability and adaptability for parenteral use are obtained bydissolving or suspending the active compound in a vehicle consisting ofa polyhydric aliphatic alcohol or mixtures thereof. Especiallysatisfactory are glycerin, propylene glycol and polyethylene glycols.The polyethylene glycols consist of a mixture of non-volatile, normallyliquid polyethylene glycols which are soluble in both water and organicliquids and which have molecular weights of from about 200 to 1500.Although the amount of active compound dissolved or suspended in theabove vehicle may vary the amount of active substance in the compositionis such that dosage in the range of about 10 to 500 mg. of compound isobtained. Although various mixtures of the aforementioned non-volatilepolyethylene glycols may be employed, it is preferred to use a mixturehaving an average molecular weight of from about 200 to about 400.

In addition to the active compound, the parenteral solutions orsuspensions may also contain various preservatives which may be used toprevent bacterial and fungal contamination. The preservatives which maybe used for these purposes are, for example, myristyl-gamma-picoliniumchloride, benzalkonium chloride, phenethyl alcohol,p-chlorophenyl-α-glycerol ether, methyl and propyl parabens andthimerosal. As a practical matter, it is also convenient to employantioxidants, such as, for example, sodium bisulfite, sodiummetabisulfite and sodium formaldehyde sulfoxylate. Generally, from about0.05 to about 0.2% concentrations of antioxidant are employed.

The active compounds of the present invention may be orallyadministered, for example, with an inert diluent or with an assimilableedible carrier, or they may be enclosed or hard or soft shell gelatincapsules, or they may be compressed into tablets, or they may beincorporated directly with the food of the diet. For oral therapeuticadministration, the active compounds may be incorporated with excipientsand used in the form of tablets, troches, capsules, suspensions, syrups,wafers and the like. Such compositions and preparations should containat least 0.1% of active compound. The percentage of the compositions andpreparations may, of course, be varied and may conveniently be betweenabout 2% to about 60% of the weight of the unit. The amount of activecompound in such therapeutically useful compositions is such that asuitable dosage will be obtained.

The tablets, troches, pills, capsules and the like may also contain thefollowing: a binder such as gum tragacanth, accia, corn starch orgelatin; excipients such as dicalcium phosphate; a disintegrating agentsuch as corn starch, potato starch, alginic acid and the like; alubricant such as magnesium stearate; and a sweetening agent such assucrose or lactose may be added or a flavoring agent such as peppermint,oil of wintergreen, or cherry flavoring. When the dosage unit form is acapsule, it may contain, in addition to materials of the above type, aliquid carrier such as a fatty oil. Various other materials may bepresent as coatings or to otherwise modify the physical form of thedosage unit. For instance, tablets, pills or capsules may be coated withshellac, sugar or both. A syrup or suspension may contain the activecompound, sucrose as a sweetening agents, methyl and propyl parabens aspreservatives, a dye and flavoring such as cherry or orange flavor. Ofcourse, any material used in preparing any dosage unit form should bepharmaceutically pure and substantially non-toxic in the amountsemployed.

The novel compounds of formula (III) of the present invention may beprepared in accordance with the following reaction scheme: ##STR4##wherein R₃, R₄, R₅ and HETEROARYL are as hereinbefore defined; X ischloro, bromo, iodo, --S--R or --SO₂ R; wherein R is alkyl having 1-4carbon atoms, phenyl, p-tolyl, benzyl, p-methoxybenzyl and the like; andY is the carbonyl activating residue of a peptide coupling reagent or agroup of the formulae: ##STR5## wherein R' is hydrogen, alkyl having 1-4carbon atoms, phenyl, p-tolyl, p-methoxybenzyl, 2,4,6-trimethylbenzyl,trimethylsilyl, 2-trimethylsilylethyl and the like or a suitablecarbonyl protecting group; and R₅ is as hereinbefore defined.

In accordance with the above reaction scheme, the carboxyl group of anappropriately substituted ω-heteroaroylalkanoic acid (IV) is convertedto a carbonyl activated derivative (V) or in accordance with thereaction scheme, derivatives (VI) (Y═OH) and (VII) (Y═OH) are convertedto carbonyl activated derivatives. The carbonyl activated derivatives of(V), (VI) and (VII) are prepared by reaction of the free acids understandard reaction conditions for activating the carboxyl groups ofN-protected aminoacids. For example, mixed anhydrides are prepared insitu by treatment of the free acids with bases such as trialkylamines(triethylamino and the like), N-methylmorpholine, pyridine,N-methylpiperidine and the like to give the amine salts which arereacted with lower alkyl chloroformates such as ethyl chloroformate,t-butyl chloroformate, isobutyl chloroformate, benzyl chloroformate,trityl chloroformate and the like. Alternatively, the free acids arereacted with N,N'-carbonyldiimidazole or related peptide couplingreagents such as N,N'-carbonyl-1,2,4-triazole to form activated carbonylderivatives. Derivatives where Y is O-hydroxysuccinimide orO-hydroxyphthalimide are prepared by reaction of the free acids withN-hydroxysuccinimide or N-hydroxyphthalimide in the presence of acarbodiimide such as N,N-dicyclohexylcarbodiimide. Derivatives wherein Yis a residue of a peptide coupling reagent or an activated ester arereacted with L-proline or L-proline derivatives under conventionalcoupling conditions.

The amides are obtained by reacting an acid halide of (IV) or preferablya carbonyl activated derivative (V) with L-proline or an ester ofL-proline such as an alkyl (C₁ -C₄) ester, benzyl ester,2,4,6-trimethylbenzyl ester and other L-proline derivatives with aprotected acid function which is removed in a later step. The reactionconditions for the formation of the carboxyl activated derivatives andconditions for coupling to L-proline or L-proline derivatives, such astime, temperature, solvents, etc. are well known in the art. In generalthe reactions are carried out at 0° C. to 50° C. in solvents such astetrahydrofuran, dioxane, N,N-dimethylformamide, dimethylsulfoxide,toluene, acetonitrile and the like for 1-24 hours.

Further elucidation of the meaning of the terms employed herein isafforded by the following table wherein typical peptide couplingreagents are listed in the left column and the corresponding carbonylactivating residues are listed in the right column:

    ______________________________________                                        Reagent           Y                                                           ______________________________________                                        N-hydroxyphthalimide                                                                             ##STR6##                                                   dicyclohexylcarbodiimide                                                                         ##STR7##                                                   N,N'-carbonyldiimidazole                                                                         ##STR8##                                                   benzyl chloroformate                                                                             ##STR9##                                                   N-hydroxysuccinimide                                                                             ##STR10##                                                  activated ester   SAryl                                                       mixed anhydride                                                                                  ##STR11##                                                  ______________________________________                                    

Numerous other peptide coupling reagents are available and well known tothe art such as unsaturated ethers, α-chlorovinyl ethyl ether,ethoxyacetylene, ketenimines and ketenes, ynamines, acyloxyphosphoniumions, EEDQ, silicon tetrachloride, 1,2-oxazolium salts, and the like.These all provide a carbonyl activating residue (--Y) and may be readilyused for the conversion of (VI) to (V) when Y is to be a "carbonylactivating residue of a peptide coupling reagent". The reactionconditions for such conversions are well known in the art and may bereadily found in such literature references as SYNTHESIS, September1972, pages 453-463 by Klausner & Bodansky.

The conversion of the intermediates (V) to the corresponding3-(X-substituted)propionic acid derivative (VI) wherein X consists ofthe hereinabove defined leaving groups is readily achieved byconventional methods well known in the art. For example, the chloro,bromo and iodo derivatives may be prepared by treating a compound offormula (V) with a halogenating agent such as chlorine, bromine,N-iodosuccinimide, and the like in a solvent such as chloroform, carbontetrachloride, acetic acid or dioxane at 25°-75° C. for 12-24 hours.Those compounds wherein X is --S--R may be obtained from the haloderivatives by treatment with an alkali metal mercaptide under standardconditions. The corresponding derivatives wherein X═SO₂ R may beobtained by oxidation of the corresponding mercapto derivatives withoxidizing agents such as meta-periodic acid and the like in an inertsolvent at 10°-100° C. for 1-24 hours. As desired, theω-heteroaroylalkanoic acids (IV) may be coupled to an L-prolinederivative ##STR12## to give intermediates (V) which are then convertedto products (III) through intermediates (VI) and (VII). Alternatively,intermediates (V) wherein Y is a carboxyl protecting group may beconverted to intermediates (VI) and (VII) at which point the protectinggroup may be removed and the intermediates (VI) or (VII) (Y═OH) coupledto L-proline or L-proline derivatives.

The ω-heteroaroylalkanoic acids (IV) wherein R₄ is other than hydrogenhave one asymmetric carbon atom and the D and L isomers may be preparedby resolution of the racemic mixture. Activation of the carboxyl groupof the resolved isomers then gives compounds of structure (V) whereinthe carbon atom bearing the R₄ group has either the D or the Lconfiguration. Conversion of the resolved compounds of structure (V) tothe reactive intermediates (VI) gives compounds which arediastereoisomers. Each diastereoisomer may then be converted tocompounds of structure (VII) as shown in the reaction scheme.Alternatively, racemic compounds of structure (IV) wherein R₄ is loweralkyl may be coupled to L-proline or L-proline derivatives to givecompounds of structure (V) which exist as diastereoisomeric forms andmay be separated by conventional means. For example, thediastereoisomeric forms of 1-[3-(2-thenoyl)-2-methylpropionyl]-L-prolinemay be separated by preferential crystallization of one diastereoisomerand isolation of the other diastereoisomer from the mother liquors. Inthis manner diastereoisomeric forms of structural type (VI) may beprepared and converted to the compounds of structure (III) which areinhibitors of the angiotension converting enzyme. The reactiveintermediates (VI) are reacted with the anion of a thioacid of formula##STR13## wherein R₈ is phenyl, alkyl having up to 3 carbon atoms orother thiolating reagents (H-R₃). Suitable anions of thioacids andthiolating reagents useful in the displacement reaction are those fromalkali metals (K⁺, Na⁺), alkaline earth metals such as calcium andmagnesium, and organic bases such as ammonia, trialkylamines, and thelike. Removal of the acyl group by reaction with hydroxylamine, ammoniumhydroxide or dilute inorganic bases gives the compounds of structure(III) wherein R₃ is mercapto. Under appropriate conditions intermediates(VI) and (VII) wherein X is --S--R and ##STR14## may be converteddirectly to products (III) wherein R₃ is --SH by removal of a thioprotecting group. For example, derivatives wherein R is a thioprotecting group such as t-butyl, p-methoxybenzyl, PhCH₂ O₂ CS-- and thelike may be deblocked under acidic conditions [HBr-HOAc, CF₃ CO₂ H, (CF₃CO₂)₂ Hg and the like] known to the art.

Derivatives (VII) wherein ##STR15## and R₃ is as previously defined andR' is a carboxyl protecting group may be converted to product (III) (R₅═H) by removal of the carboxyl protecting group under conventionalconditions. In general carboxyl protecting groups which are removedunder acidic conditions are preferred. For example, t-butyl esters arecleaved by treatment with trifluoroacetic acid or aqueoustrifluoroacetic acid at 0° C. to 50° C. for 1-24 hours. Trimethylsilyland 2-trimethylsilylethyl are removed under conventional conditionsknown to the art. The reactions illustrated in the reaction scheme maybe carried out with esters (R₅ ═lower alkyl) to give the products (III)wherein R₅ is lower alkyl. In the products (III) (wherein R₅ istert-butyl) the ester group may be removed in the presence oftrifluoroacetic acid to give the free acid derivatives of (III).

The novel compounds of formula (I) of the present invention may beprepared in accordance with the following reaction scheme: ##STR16## andthe novel compounds of formula (II) of the present invention may beprepared in accordance with the following reaction scheme: ##STR17##wherein R₁, R₂, R₃, R₅, HETEROARYL and Y are as hereinbefore defined. Inaccordance with the above reaction schemes, an appropriately substitutedω-heteroaroylacrylic acid (VIII), ω-heteroaroylcrotonic acid (XI) or3-heteroaroyl-3-butenoic acid (XIV) is converted to a carbonyl activatedderivative (IX), (XII) or (XV). The reaction conditions for theformation of such carbonyl activated derivatives such as time,temperature, solvents, etc. are well known in the art and arehereinbefore discussed for the conversion of (IV) to products (III). Thecarboxyl activated derivatives (IX), (XII) and (XV) are prepared bytreatment of the free acids (VIII), (XI) or (XIV) with peptide couplingreagents as hereinbefore discussed. (See table of carbonyl activatingresidues).

Derivatives (IX), (XII) or (XV) wherein Y is a residue of a peptidecoupling reagent or an activated ester are reacted with L-proline or anL-proline derivative of the formulae: ##STR18## wherein R' and R₅ are aspreviously defined to give intermediates containing a double bond inconjugation with a carbonyl group. The intermediates (IX), (XII) and(XV) are reacted with a thiolating reagent which gives the products (I)or (II) directly or intermediates (X) or (XIII) convertible intoproducts (I) or (II). The position of the double bond determines thedirection of the 1,4-addition of the thiolating reagent as shown in thereaction scheme. Thiolating reagents add 1,4 to the ketone carbonyl ofintermediates (VIII), (IX), (XIV) and (XV) while addition occurs 1,4 tothe carboxyl group in derivatives (XI) and (XII). Suitable thiolatingreagents are H₂ S, H-S-C(CH₃)₃, and H-R₃ wherein R₃ is as hereinbeforedefined. Preferred reagents are hydrogen sulfide or a thiolating agentof the formula: ##STR19## wherein R₈ is phenyl or alkyl having up to 3carbon atoms.

The preferred conditions for the addition of a thiolating reagent arereaction in inert solvents such as chloroform, dichloromethane, carbontetrachloride, dimethylformamide, tetrahydrofuran, dioxane,acetonitrile, toluene, lower alkanols and the like at 0° C. to 100° C.for 1-24 hours. Conversion of compounds (X) and (XIII) wherein Y is agroup of the formula: ##STR20## and R' is a carboxyl protecting group aspreviously defined is carried out by removal of the protecting group togive products (I) and (II) wherein R₅ ═H. Carboxyl protecting groupswhich are removed under acidic conditions are preferred. The reactionsillustrated in the reaction scheme may be carried out with esters ofL-proline (R₅ ═lower alkyl) to give the products (I) and (II) wherein R₅is lower alkyl. In the products wherein R₅ is tert-butyl the ester groupmay be removed in the presence of trifluoroacetic acid or aqueoustrifluoroacetic acid to give the free acid derivatives of (I) and (II).Conversion of compounds of formulae (X) and (XIII) to final products (I)and (II) is achieved as set forth hereinbefore for the conversion of(VII) to (III). Derivatives which contain a thio protecting group may beconverted to products (I) or (II) wherein R₃ is --SH by removing theprotecting group under conventional conditions.

The invention will be described in greater detail in conjunction withthe following specific examples.

EXAMPLE 1 1-[3-(Acetylthio)-3-(2-thenoyl)propionyl]-L-proline

A solution of 0.3 mole of thiophene in 100 ml. of nitrobenzene is addeddropwise with stirring to a cooled mixture of 30 g. (0.3 mole) ofsuccinic anhydride, 87.8 g. (0.66 mole) of aluminum chloride and 300 ml.of nitrobenzene. The mixture is cooled and stirred for 30 minutes andthen allowed to stand at room temperature overnight. The mixture ispoured onto ice and 50 ml. of concentrated hydrochloric acid. Thenitrobenzene is removed by steam distillation. The aqueous layer isdecanted and the residue is mixed with 650 ml. of water and 20 g. ofsodium carbonate. The mixture is heated, mixed with diatomaceous earthand filtered. The filtrate is acidified with concentrated hydrochloricacid and the solid which separates is filtered and washed with water.Recrystallization from water gives 53% of 4-oxo-4-(2-thienyl)butyricacid, m.p. 121°-123° C.

The preceding compound (0.02 mole), 1,1'-carbonyldiimidazole (0.021mole) and 25 ml. of tetrahydrofuran is stirred at room temperature forone hour. To the mixture is added 0.025 mole of L-proline and themixture is stirred at room temperature for 16 hours and refluxed for onehour. The mixture is diluted with a little water and the solvent removedunder reduced pressure. The residue is partitioned betweendichloromethane, water and 0.04 ml. of concentrated hydrochloric acid.The dichloromethane layer is separated, washed with water, dried overmagnesium sulfate and concentrated under reduced pressure to give 85% of1-[3-(2-thenoyl)propionyl]-L-proline as crystals, m.p. 100°-102° C.

To a mixture of 0.008 mole of the preceding compound, 50 ml. of glacialacetic acid and one drop of fuming hydrogen bromide is added dropwise0.008 mole of bromine in 25 ml. of glacial acetic acid. The mixture isstirred at room temperature overnight and the solvent removed underreduced pressure. The residue is dissolved in dichloromethane, and thesolution is washed with water and dried over magnesium sulfate. Thesolvent is removed in vacuo to yield 53% of1-[3-bromo-3-(2-thenoyl)propionyl]-L-proline as a glass.

A mixture of the preceding compound (0.0085 mole) in 25 ml. of ethanolis added to a mixture of 0.81 g. (0.015 mole) of sodium methoxide, 1.07ml. (0.015 mole) of thioacetic acid and 25 ml. of ethanol. The resultingmixture is stirred at room temperature for 16 hours, the solvent isremoved under reduced pressure and the residue is partitioned betweendichloromethane and water containing acetic acid. The organic layer isseparated, washed with water and dried over magnesium sulfate. Thesolvent is removed in vacuo to give an 84% yield of the product of theExample as a glass.

EXAMPLE 2 1-[3-(Acetylthio)-3-(5-bromo-2-thenoyl)propionyl]-L-proline

As described for Example 1, 0.3 mole of 2-bromothiophene is reacted withsuccinic anhydride to give 4-(5-bromo-2-thienyl)-4-ketobutyric acid(51%), m.p. 141°-143° C. The preceding compound is coupled to L-prolineto give 1-[3-(5-bromo-2-thenoyl)propionyl]-L-proline (56%) as crystals,m.p. 166°-168° C. The preceding compound (0.008 mole) is reacted withbromine in acetic acid to yield1-[3-bromo-3-(5-bromo-2-thenoyl)propionyl]-L-proline as a glass (97%).As for Example 1, reaction of the preceding compound with sodiumthioacetate gives the product of the Example (88%) as a yellow glass.

EXAMPLE 3 1-[3-(Acetylthio)-3-(5-chloro-2-thenoyl)propionyl]-L-proline

As described for Example 1, 0.3 mole of 2-chlorothiophene is reactedwith succinic anhydride to give 4-(5-chloro-2-thienyl)-4-ketobutyricacid (74%), m.p. 121°-123° C. The preceding compound is coupled toL-proline to give 1-[3-(5-chloro-2-thenoyl)propionyl]-L-proline (94%) ascrystals, m.p. 131°-133° C. The above compound is reacted with brominein acetic acid to give1-[3-bromo-3-(5-chloro-2-thenoyl)-propionyl]-L-proline as a glass. Asfor Example 1, reaction of the preceding compound with sodiumthioacetate in ethanol gives the desired product (84%) as a glass.

EXAMPLE 41-[3-(Acetylthio)-3-(benzo[b]thien-3-ylcarbonyl)propionyl]-L-proline

As described in Example 1, 0.30 mole of thionaphthene is reacted withsuccinic anhydride to give a mixture ofγ-oxo-benzo[b]thiophene-3-butyric acid, m.p. 138°-142° C. andγ-oxo-benzo[b]thiophene-2-butyric acid, m.p. 175° C.

The γ-oxo-benzo[b]thiophene-3-butyric acid is coupled to L-proline with1,1'-carbonyldiimidazole to give1-[3-(benzo[b]thien-3-ylcarbonyl)propionyl]-L-proline (78%) as a glass.As for Example 1, the preceding compound is reacted with bromine inacetic acid to give1-[3-bromo-3-(benzo[b]thien-3-ylcarbonyl)propionyl]-L-proline as a glass(97%). Reaction with sodium thioacetate in ethanol gives the product(92%) of the Example as a glass.

EXAMPLE 51-[3-(Acetylthio)-3-(benzo[b]thien-2-ylcarbonyl)propionyl]-L-proline

As for Example 4, γ-oxo-benzo[b]thiophene-2-butyric acid is coupled toL-proline. The coupled product is brominated and reacted with sodiumthioacetate to give the product of the Example as a glass.

EXAMPLE 6 1-[3-(Acetylthio)-3-(2-thenoyl)-2-methylpropionyl]-L-proline

To a mixture of 180.7 g. of p-toluenesulfonic acid in 500 ml. oftetrahydrofuran is added slowly 170 g. of morpholine. To this mixture isadded 100 g. of 2-thiophenecarboxaldehyde and the resulting mixture isrefluxed for 18 hours. The reaction mixture is cooled and a mixture of65.1 g. of potassium cyanide in 100 ml. of water is added. The mixtureis refluxed for 48 hours and the solvent removed under reduced pressure.The residue is dissolved in chloroform and the organic layer washed withwater, sodium bisulfite solution and brine. The chloroform extract isdried over magnesium sulfate and filtered through a pad of hydratedmagnesium silicate. The filtrate is concentrated and the residue istriturated with hexane to give 162 g. ofα-2-thienyl-4-morpholineacetonitrile, m.p. 78°-79° C.

The preceding compound in tetrahydrofuran is reacted withmethyacrylonitrile in the presence of 30% potassium hydroxide inethanol. The product is hydrolysed with 6 N hydrochloric acid to give3-(2-thenoyl)-2-methylpropionic acid.

The preceding compound is coupled with L-proline as described in Example1 to give 1-[3-(2-thenoyl)-2-methylpropionyl]-L-proline (mixture ofdiastereomers). The [R]-1-[3-(2-thenoyl)-2-methylpropionyl]-L-proline isreacted with bromine in acetic acid and the brominated product isreacted with sodium thioacetate in acetonitrile to give a mixture of[S-(R*,S*)]-1-[3-acetylthio-3-(2-thenoyl)-2-methylpropionyl]-L-prolineand[S-(R*,R*)]-1-[3-acetylthio-3-(2-thenoyl)-2-methylpropionyl]-L-prolineas a glass.

EXAMPLE 71-[3-Acetylthio-3-(5-chloro-2-thenoyl)-2-methylpropionyl]-L-proline

As for Example 1, 3-(5-chloro-2-thenoyl)-2-methylpropionic acid isreacted with L-proline to give1-[3-(5-chloro-2-thenoyl)-2-methylpropionyl]-L-proline. The mixture ofdiastereomers is separated. Bromination of[R]-1-[3-(5-chloro-2-thenoyl)-2-methylpropionyl]-L-proline and reactionof the brominated product with sodium thioacetate in acetonitrile givesa mixture of [S-(R*,S*)] and [S-(R*,R*)] isomers of the product of theExample as a glass.

Bromination of the[S]-1-[3-(5-chloro-2-thenoyl)-2-methylpropionyl]-L-proline and reactionof the brominated product with sodium thioacetate in acetonitrile givesa mixture of the [R-(R*,S*)] and [R-(R*,R*)] isomers of the product ofthe Example as a glass.

EXAMPLE 8 1-[3-Acetylthio-3-(3-thenoyl)-propionyl]-L-proline

As for Example 6, 99 g. of 3-thiophenecarboxaldehyde is converted toα-(3-thienyl)-4-morpholineacetonitrile (137 g.; m.p. 85°-87° C.). Thepreceding compound 50.5 g. is reacted with 100 ml. of ethyl acrylate in500 ml. of tetrahydrofuran in the presence of 50 ml. of 30% potassiumhydroxide in ethanol. The solvent is removed from the reaction mixtureand the residue is heated with 6 N hydrochloric acid to give3-(3-thenoyl)propionic acid. As for Example 1, the preceding compound isconverted to the product of the Example to give a glass.

EXAMPLE 9 1-[3-Acetylthio-3-(3-thenoyl)-2-methylpropionyl]-L-proline

As for Example 8, α-(3-thienyl)-4-morpholineacetonitrile is reacted withmethacrylonitrile and the resulting product is refluxed with 6 Nhydrochloric acid to give 3-(3-thenoyl)-2-methylpropionic acid. As forExample 1, the preceding compound is coupled with L-proline to give1-[3-(3-thenoyl)-2-methylpropionyl]-L-proline. The preceding product isreacted with bromine in acetic acid and the brominated product isreacted with sodium thioacetate in acetonitrile to give the product ofthe Example as a glass (mixture of diastereomers).

EXAMPLE 10 1-[3-Acetylthio-3-(5-chloro-3-thenoyl)propionyl]-L-proline

As for Example 8, 3-(5-chloro-3-thenoyl)propionic acid is coupled toL-proline with 1,1'-carbonyldiimidazole. The coupled product is reactedwith bromine in acetic acid and the brominated derivative is reactedwith sodium thioacetate in acetonitrile to give the product of theExample as a glass.

EXAMPLE 11 1-[3-Acetylthio-3-(2-pyridylcarbonyl)propionyl]-L-proline

To a solution of 3.58 g. of γ-oxo-2-pyridinebutyric acid, m.p. 67°-80°C. and 2.30 g. of N-hydroxysuccinimide in 25 ml. of dioxane is added asolution of 4.12 g. of N,N-dicyclohexylcarbodiimide in 25 ml. ofdioxane. The mixture is stirred for 18 hours at room temperature andfiltered. The filtrate is concentrated under reduced pressure. Theresidue is triturated with hexane to give 5.3 g. of tan solid. The solidis recrystallized by dissolving in 50 ml. of methylene chloride. Thesolution is diluted with 50 ml. of hexane, then chilled and filtered togive 3.1 g. of γ-oxo-2-pyridinebutyric acid, N-hydroxysuccinimide esteras crystals, m.p. 143°-145° C.

The preceding compound (3.1 g.) as a slurry in 60 ml. of ethanol isadded to a mixture of 1.9 g. of L-proline and 2.75 g. of sodiumbicarbonate in 60 ml. of water. The mixture is stirred at roomtemperature for 48 hours, then concentrated to 1/2 its volume. Themixture is chilled (ice bath) and acidified by dropwise addition ofconcentrated hydrochloric acid. The mixture is extracted with ethylacetate. The extract is dried over magnesium sulfate and concentrated togive 1.06 g. of 1-[3-(2-pyridylcarbonyl)propionyl]-L-proline as a gum.The preceding compound (0.276 g.) is dissolved in 5 ml. of glacialacetic acid and 0.16 g. of bromine in 2 ml. of acetic acid is added. Themixture is stirred at room temperature for 2 hours and the solventremoved. The residue is reacted with sodium thioacetate in acetonitrilefor 4 hours to give the product of the Example as a glass.

EXAMPLE 12 1-[3-Acetylthio-3-(3-pyridylcarbonyl)propionyl]-L-proline

As for Example 11, γ-oxo-3-pyridinebutyric acid is coupled to L-prolineto give 1-[3-(3-pyridylcarbonyl)propionyl]-L-proline.

Bromination with bromine in acetic acid and reaction of the brominatedderivative with sodium thioacetate in acetonitrile gives the product ofthe Example as a glass.

EXAMPLE 13 1-[3-Acetylthio-3-(2-pyridylcarbonyl)propionyl]-L-proline,pyridine-1-oxide

As for Example 11, γ-oxo-2-pyridinebutyric acid, pyridine-1-oxide iscoupled to L-proline to give1-[3-(2-pyridylcarbonyl)propionyl]-L-proline, pyridine-1-oxide. Reactionof the preceding compound with bromine in acetic acid and reaction ofthe brominated compound with sodium thioacetate in acetonitrile givesthe product of the Example as a glass.

EXAMPLE 14 1-[3-Acetylthio-3-(3-indolylcarbonyl)propionyl]-L-proline

As for Example 1, 4-oxo-4-(3-indolyl)butyric acid (0.1 mole) is coupledto L-proline to give 1-[3-(3-indolylcarbonyl)propionyl]-L-proline. Thepreceding compound is reacted with bromine in acetic acid and thebrominated derivative is reacted with sodium thioacetate in acetonitrileto give the product of the Example as a glass.

EXAMPLE 151-[3-Acetylthio-3-(1-methyl-3-indolylcarbonyl)propionyl]-L-proline

As for Example 11, the N-hydroxysuccinimide ester of3-(1-methyl-3-indolylcarbonyl)propionic acid is prepared and coupled toL-proline to give 1-[3-(1-methyl-3-indolylcarbonyl)propionyl]-L-proline.The preceding compound is reacted with bromine in acetic acid and thebrominated derivative reacted with sodium thioacetate in acetonitrile togive the product of the Example as a glass.

EXAMPLE 16 1-[3-Acetylthio-3-(3-pyrazolylcarbonyl)propionyl]-L-proline

Substitution of 3-pyrazolecarboxaldehyde for 2-thiophenecarboxaldehydein Example 6 gives the product of the Example.

EXAMPLE 171-[3-Acetylthio-3-(5-methyl-3-pyrazolylcarbonyl)-propionyl]-L-proline

Substitution of 5-methyl-3-pyrazolecarboxaldehyde for2-thiophenecarboxaldehyde in Example 6 gives the product of the Example.

EXAMPLE 18 1-[3-Acetylthio-3-(4-pyrimidylcarbonyl)propionyl]-L-proline

Substitution of 4-pyrimidinecarboxaldehyde for 2-thiophenecarboxaldehydein Example 6 gives the product of the Example.

EXAMPLE 191-[3-Acetylthio-3-(2-methyl-4-pyrimidylcarbonyl)-propionyl]-L-proline

Substitution of 2-methyl-4-pyrimidinecarboxaldehyde for2-thiophenecarboxaldehyde in Example 6 gives the product of the Example.

EXAMPLE 201-[3-Acetylthio-3-(1-methyl-2-imidazolylcarbonyl)-propionyl]-L-proline

Substitution of 1-methyl-2-imidazolecarboxaldehyde for2-thiophenecarboxaldehyde in Example 6 gives the product of the Exampleas a glass.

EXAMPLE 21 1-[3-(Benzoylthio)-3-(2-thenoyl)propionyl]-L-proline

As for Example 1, 1-[3-bromo-3-(2-thenoyl)propionyl]-L-proline (0.0085mole) in 25 ml. of acetonitrile is added to a mixture of 0.015 mole ofsodium methoxide and 0.015 mole of thiobenzoic acid in 25 ml. ofacetonitrile. The mixture is stirred at room temperature for 16 hours,one ml. of acetic acid is added and the solvent removed under reducedpressure. The residue is partitioned between dichloromethane and watercontaining acetic acid. The organic layer is separated, washed withwater, dried over magnesium sulfate and the solvent removed underreduced pressure to give the product of the Example as a pale yellowglass.

EXAMPLE 221-[3-(Benzoylthio)-3-(benzo[b]thien-3-ylcarbonyl)propionyl]-L-proline

As for Example 21,1-[3-bromo-3-(benzo[b]thien-3-ylcarbonyl)propionyl]-L-proline (0.01mole) in 25 ml. of acetonitrile is added to a mixture of 0.01 mole ofsodium methoxide and 0.015 mole of thiobenzoic acid in 25 ml. ofacetonitrile. The mixture is stirred at room temperature for 16 hours,one ml. of acetic acid is added and the solvent is evaporated in vacuo.The residue is partitioned between dichloromethane and water containingacetic acid. The organic layer is separated, washed with water and driedover magnesium sulfate. The solvent is removed in vacuo to give theproduct of the Example as a yellow glass.

EXAMPLE 23 1-[3-(Benzoylthio)-3-(5-chloro-2-thenoyl)propionyl]-L-proline

As for Example 21, 0.01 mole of1-[3-bromo-3-(5-chloro-2-thenoyl)propionyl]-L-proline is reacted withsodium thiobenzoate for 16 hours in acetonitrile to give the product ofthe Example as a glass.

EXAMPLE 241-[3-(Benzoylthio)-3-(1-methyl-2-pyrrolylcarbonyl)propionyl]-L-proline

As for Example 6, 1-methyl-2-pyrrolecarboxaldehyde is converted toα-(1-methyl-2-pyrrolyl)-4-morpholineacetonitrile. The preceding compoundis reacted with ethyl acrylate and the resulting 1,4-addition product isheated at 100° C. with 6 N hydrochloric acid to give3-(1-methyl-2-pyrrolylcarbonyl)propionic acid.

As for Example 1, the preceding compound is coupled to L-proline to give1-[3-(1-methyl-2-pyrrolylcarbonyl)propionyl]-L-proline. The precedingcompound (0.01 mole) is brominated with bromine (0.011 mole) in aceticacid and the resulting1-[3-bromo-(1-methyl-2-pyrrolylcarbonyl)propionyl]-L-proline (0.01 mole)is reacted with sodium thiobenzoate as for Example 21 to give theproduct of the Example as a glass.

EXAMPLE 25 1-[3-(Acetylthio)-3-(2-thenoyl)propionyl]-L-proline, methylester

Substituting L-proline, methyl ester for L-proline in Example 1 givesthe product of the Example as a glass.

EXAMPLE 26 1-[3-(Acetylthio)-3-(5-chloro-2-thenoyl)propionyl)-L-proline,t-butyl ester

Substituting the t-butyl ester of L-proline for L-proline in Example 3gives the product of the Example as a glass.

EXAMPLE 27 1-[2-(Acetylthio)-3-(2-thenoyl)propionyl]-L-proline

As for Example 1, 3-(2-thenoyl)acrylic acid (0.01 mole) is coupled toL-proline (0.01 mole) with N,N'-carbonyldiimidazole (0.011 mole) intetrahydrofuran to give 1-[3-(2-thenoyl)acryloyl]-L-proline.

A mixture of the preceding compound (0.01 mole) and thioacetic acid(0.03 mole) in carbon tetrachloride is refluxed for 3 hours. The solventis removed in vacuo to give the product of the Example as a glass.

EXAMPLE 281-[2-Acetylthio)-3-(benzo[b]thien-3-ylcarbonyl)propionyl]-L-proline

As for Example 1, 3-(benzo[b]thien-3-ylcarbonyl)acrylic acid (0.01 mole)is coupled to L-proline (0.01 mole) with N,N'-carbonyldiimidazole intetrahydrofuran to give1-[3-(benzo[b]thien-3-ylcarbonyl)acryloyl]-L-proline.

A mixture of the preceding compound (0.01 mole) and thioacetic acid(0.03 mole) in carbon tetrachloride is refluxed for 2 hours. The solventis removed in vacuo to give the product of the Example as a glass.

EXAMPLE 29 1-[2-Acetylthio-3-(3-puridylcarbonyl)propionyl]-L-proline

As for Example 27, 3-(3-pyridylcarbonyl)acrylic acid (0.01 mole) isreacted with N,N'-carbonyldiimidazole (0.011 mole) in tetrahydrofuranand to the mixture is added 0.011 mole of L-proline. The mixture isrefluxed 16 hours and the solvent removed under reduced pressure. Themixture is partitioned between dichloromethane and water containingacetic acid. The organic layer is separated, washed with water and driedover magnesium sulfate. The solvent is removed in vacuo to yield1-[3-(3-pyridylcarbonyl)acryloyl]-L-proline. The preceding compound isdissolved in carbon tetrachloride and 0.03 mole of thioacetic acid isadded. The mixture is heated 3 hours and the solvent is removed in vacuoto give the product of the Example as a glass.

EXAMPLE 301-[2-Acetylthio-3-(1-methyl-3-indolylcarbonyl)propionyl]-L-proline

As for Example 29, 3-(1-methyl-3-indolylcarbonyl)acrylic acid is coupledto L-proline to give1-[3-(1-methyl-3-indolylcarbonyl)acryloyl]-L-proline.

A mixture of 0.01 mole of the preceding compound, and 0.03 mole ofthioacetic acid in methanol is refluxed for 4 hours. The solvent isremoved to give the product of the Example as a glass.

EXAMPLE 311-[2-Acetylthio-3-(1-methyl-4-pyrazolylcarbonyl)propionyl]-L-proline

As for Example 29, 3-(1-methyl-4-pyrazolylcarbonyl)acrylic acid iscoupled to L-proline and the resulting1-[3-(1-methyl-4-pyrazolylcarbonyl)acryloyl]-L-proline is reacted withthioacetic acid to give the product of the Example as a glass.

EXAMPLE 32 1-[3-Acetyl-3-(2-quinolylcarbonyl)propionyl]-L-proline

As for Example 6, 3-(2-quinolylcarbonyl)propionic acid (0.01 mole) iscoupled to L-proline (0.011 mole) with 1,1'-carbonyldiimidazole (0.01mole) in tetrahydrofuran to give1-[3-(2-quinolylcarbonyl)propionyl]-L-proline. Bromination of thepreceding compound and reaction of the resulting compound with sodiumthioacetate gives the product of the Example.

EXAMPLE 33 1-[3-Acetylthio-4-(2-thenoyl)butyryl]-L-proline

To a mixture of 0.01 mole of 4-(2-thenoyl)crotonic acid in 50 ml. oftetrahydrofuran is added 0.011 mole of N,N'-carbonyldiimidazole. Afterstirring for 2 hours, L-proline (0.01 mole) is added and the mixture isstirred for 24 hours at room temperature and refluxed for one hour togive 1-[4-(2-thenoyl)crotonyl]-L-proline.

A mixture of the preceding compound and 0.03 moles of thioacetic acid indichloromethane is refluxed for 10 hours to give the product of theExample as a glass.

EXAMPLE 34

1-[3-Acetylthio-4-(2-furoyl)butyryl]-L-proline

To a mixture of 0.02 moles of 4-(2-furoyl)crotonic acid in 100 ml. oftetrahydrofuran is added 0.022 moles of N,N'-carbonyldiimidazole. Themixture is stirred for 3 hours at room temperature and 0.021 moles ofL-proline are added. The mixture is refluxed 2 hours and stirred at roomtemperature for 16 hours to give 1-[4-(2-furoyl)crotonyl]-L-proline.

A mixture of the preceding compound and 0.04 moles of thioacetic acid indichloromethane is refluxed for 10 hours to give the product of theExample as a glass.

EXAMPLE 351-[3-Acetylthio-3-(benzo[b]thien-2-ylcarbonyl)-2-methylpropionyl]-L-proline

To a solution of 2.68 g. (0.020 mole) of benzo[b]-thiophene in 40 ml. ofether cooled at -20° C. is added 0.020 moles of n-butyl lithium (2.54 Nsolution in hexane). The mixture is stirred at -20° C. for 15 minutes,then is allowed to warm to room temperature. Then 2.70 g. (0.020 mole)of N-methylformamilide is added and the mixture is stirred for 24 hours.The reaction is quenched with water and the mixture is treated withsaturated sodium bisulfite solution. The bisulfite addition product iscollected by filtration. The wet cake is slurried in water anddecomposed by the addition of solid sodium carbonate. The mixture isfiltered and the solid is washed with water and dried to give 1.75 g. ofbenzo[b]thiophene-2-carboxaldehyde.

To a solution of 47.0 g. of the preceding compound (prepared asdescribed above) in 250 ml. of tetrahydrofuran is added 60.5 g. ofp-toluenesulfonic acid hydrate followed by 55.0 g. of morpholine in 60ml. of tetrahydrofuran. The reaction mixture is refluxed for one hourand cooled to 40° C. A slurry of 20.4 g. of potassium cyanide in 16 ml.of water is added and the mixture is refluxed for an additional 20hours. The solvent is removed in vacuo and the residue is partitionedbetween chloroform and water. The organic layer is washed with saturatedsodium bisulfite solution, then with brine, dried over magnesiumsulfate, treated with activated charcoal, filtered and concentrated togive a brown oil which is crystallized from chloroform-hexane to give62.1 g. of α-(benzo[b]thien-2-yl)-4-morpholineacetonitrile.

To a solution of 56.8 g. of the preceding compound in 40 ml. oftetrahydrofuran is added 5 ml. of 30% potassium hydroxide in methanol,the solution turns dark brown. Then 22.0 ml. of methacrylonitrile isadded (exothermic reaction) with stirring and the solution darkensfurther to a dark violet. Stirring is continued at ambient temperaturefor 20 hours. The mixture is concentrated in vacuo to a brown-violet oilwhich is taken up in chloroform and passed through hydrous magnesiumsilicate with chloroform as eluent. The eluent is concentrated and theresidue is crystallized from cyclohexane/dichloromethane to give 60.9 g.of 4-[benzo[b]thien-2-yl]-2-methyl-4-morpholinoglutaronitrile as asolid.

A mixture of 16.98 g. of the above compound, 120 ml. of acetic acid and8.0 ml. of water is heated at 100° C. for 18 hours. The mixture isconcentrated in vacuo and the residue is dissolved in dichloromethane.This solution is passed through hydrous magnesium silicate withdichloromethane as eluent. The eluent is evaporated in vacuo and theresidue is crystallized from chloroform-hexane to give 8.60 g. of3-(benzo[b]thien-2-ylcarbonyl)-2-methylpropionitrile.

A mixture of 21.5 g. of the preceding compound (prepared as described)and 400 ml. of 6 N hydrochloric acid is refluxed for 24 hours. Themixture is cooled and then extracted with chloroform. The extracts arecombined and passed through hydrous magnesium silicate with chloroformas eluent. The eluent is evaporated to give 21.1 g. of3-(benzo[b]thien-2-ylcarbonyl)-2-methylpropionic acid.

To a solution of 19.67 g. of the above compound in 400 ml. oftetrahydrofuran is added 13.49 g. of N,N'-carbonyldiimidazole. Themixture is stirred for 4 hours, then 9.11 g. of L-proline is added andstirring is continued for 19 hours longer at room temperature. Themixture is concentrated in vacuo and the residue is partitioned betweenchloroform and water. The organic layer is washed with 2 N hydrochloricacid, dried over anhydrous sodium sulfate and evaporated in vacuo togive 1.83 g. of product as a viscous gum. The above aqueous layer isreextracted with chloroform to obtain an additional 2.39 g. of productto give a total yield of 4.22 g. of1-[3-(benzo[b]thien-2-ylcarbonyl)-2-methylpropionyl]-L-proline.

To a solution of 4.22 g. of the preceding compound in 60 ml. of glacialacetic acid is added 2 drops of fuming hydrogen bromide, followed by thedropwise addition of a solution of 1.95 g. of bromine in 10 ml. ofglacial acetic acid over a period of 25 minutes. The mixture is stirredfor an additional 3 hours then the solvent is removed in vacuo. Theresidue is dissolved in 10 ml. of ethanol and is added to a solution of0.95 g. of thiolacetic acid and 0.69 g. of potassium hydroxide in 10 ml.of ethanol. This mixture is stirred at room temperature for 3 hours thenis filtered through diatomaceous earth. The filtrate is evaporated invacuo and the residue is partitioned between dichloromethane and watercontaining a few drops of acetic acid. The organic layer is washed withwater, dried over anhydrous sodium sulfate and evaporated to give 0.21g. of the product of the Example as a glass.

EXAMPLE 36 1-[ 3-Acetylthio-3-(2-furoyl)propionyl]-L-proline

To a mixture of 82.19 g. of 2-acetylfuran, 60.8 g. of dimethylaminehydrochloride and 22.4 g. of paraformaldehyde in 225 ml. of ethanol isadded 2.0 ml. of concentrated hydrochloric acid. The mixture is refluxedfor 15 minutes, an additional 11.2 g. of paraformaldehyde is added andthe reaction mixture is refluxed for another 1/2 hour. After standing atroom temperature for 16 hours the reaction mixture is filtered. Thesolid is washed twice with 50 ml. of alcohol to give 47.2 g. of3-dimethylamino-1-(2-furyl)-1-propanone.

The preceding compound (47.2 g.) is dissolved in 1.6 liters of water. Tothis solution is added 30.2 g. of potassium cyanide. The resultingyellow solution is refluxed for 1/2 hour, cooled to room temperature andextracted with four 200 ml. portions of chloroform. The combined extractis dried over anhydrous sodium sulfate, filtered and evaporated in vacuoto give a brown solid. The solid is recrystallized from ethanol with theaid of activated carbon to give 5.49 g. of 3-(2-furoyl)propionitrile asa brownish solid.

The above product (5.49 g.) is hydrolyzed by refluxing with 100 ml. of 6N hyrochloric acid for one hour. To the hot solution is added one gramof activated carbon. The mixture is filtered hot and the filtrate iscooled in a refrigerator for 16 hours. The precipitate formed iscollected and washed with water to give 3.52 g. of 3-(2-furoyl)propionicacid.

A mixture of the preceding compound (3.52 g.), 2.41 g. ofN-hydroxysuccinimide and 4.32 g. of dicyclohexylcarbodiimide in 50 ml.of p-dioxane is stirred at room temperature for 20 hours. The mixture isfiltered and the fine white precipitate is washed with dioxane. Thecombined filtrate and wash is evaporated in vacuo and the residue iscrystallized from hexane-dichloromethane to give 4.0 g. of theN-hydroxysuccinimide ester of 3-(2-furoyl)propionic acid as ayellow-brown solid.

To a solution of 2.57 g. of L-proline and 3.75 g. of sodium bicarbonatein 85 ml. of water is added a slurry of 4.0 g. of the preceding compoundin 85 ml. of ethanol. The reaction mixture is stirred at roomtemperature for 21 hours. The solution is concentrated to 1/2 volume invacuo, then is acidified with hydrochloric acid and extracted with four50 ml. portions of dichloromethane. The combined organic layer is driedover anhydrous sodium sulfate, filtered and evaporated in vacuo to givea yellow-orange oil. The oil is crystallized from ether to give 1.8 g.of 1-[3-(2-furoyl)propionyl]-L-proline.

To a stirred solution of 1.8 g. of the preceding product in 35 ml. ofglacial acetic acid at room temperature is added one drop of fuminghydrogen bromide, followed by the dropwise addition of a solution of1.09 g. of bromine in 15 ml. of glacial acetic acid over a 30 minuteperiod. The reaction mixture is completely decolorized after 40 minutesand is stirred for an additional 3 hours. The solution is evaporated invacuo and the residue is chromatographed in a conventional manner onpreparative thin layer chromatography plates to give 1.22 g. of1-[3-bromo-3-(2-furoyl)propionyl]-L-proline.

To a solution of 0.35 g. of thiolacetic acid in 5 ml of ethanol is added0.26 g. of potassium hydroxide. To this solution is added with stirring1.22 g. of the above compound in 5.0 ml. of ethanol. The mixture isstirred for one hour and filtered. The filtrate is evaporated to give anorange oil. Further evaporation under high vacuum gives the product ofthe Example as a glass.

EXAMPLE 371-[3-Acetylthio-3-(2-benzofuranylcarbonyl)propionyl]-L-proline

To a solution of 50.0 g. of 2-benzofuranyl methyl ketone in 200 ml. ofglacial acetic acid is added 2.0 ml. of fuming hydrobromic acid (48%),followed by the dropwise addition of a solution of 49.9 g. of bromine(16 ml.) in 30 ml. of acetic acid over a 21/2 hour period. Thetemperature of the reaction mixture is maintained at 80° C. during thisaddition and is kept at 80° C. for an additional hour, then is allowedto cool gradually to room temperature. The reaction mixture is added to2 liters of water. The aqueous layer is decanted and the residue ischromatographed on a short column of silica gel. The column is elutedwith dichloromethane. The eluent is evaporated to give a residue. Theresidue is crystallized from ethanol:isopropanol (3:17). As the hotsolution cools an oily solid separates. The supernatant is decanted andallowed to stand to crystallize the product, 17.01 g. of 2-benzofuranylbromomethyl ketone.

To a stirred solution of 7.41 g. of diethylmalonate in 100 ml. ofethanol is added 1.06 g. of sodium. The mixture is stirred until thesodium has reacted. The mixture is heated to 80° C. and 11.06 g. of2-benzofuranyl bromomethyl ketone in 100 ml. of hot ethanol is added inone portion. The mixture is refluxed for 2 hours and concentrated invacuo. The residue is dissolved in ether and is passed through a shortcolumn of hydrous magnesium silicate. The column is eluted with ether.The ether is evaporated to give a residue. To the residue is added 200ml. of water, 100 ml. of methanol and 60 ml. of 10 N sodium hydroxide.This mixture is refluxed 4 hours and cooled to room temperature. Theaqueous layer is decanted, neutralized with concentrated hydrochloricacid and heated for 2 hours on a hot plate. The mixture is allowed tocool to separate a solid. The solid is collected, washed with water andair dried. The solid is heated to its melting point (160° C.) where itdecarboxylates. The residue is crystallized with a small amount ofacetone to give 0.98 g. of 3-(2-benzofuranylcarbonyl)propionic acid.

A mixture of 1.72 g. of the preceding compound (prepared as described),0.91 g. of N-hydroxysuccinimide, 1.63 g. of dicyclohexylcarbodiimide and50 ml. of p-dioxane is stirred at room temperature for 20 hours. Theresulting solid is filtered off and washed with 20 ml. of p-dioxane. Thecombined filtrate and wash is evaporated to give a brown-orange oil. Theoil is crystallized with dichloromethane/hexane to give 1.76 g. ofN-hydroxysuccinimide ester of 3-(2-benzofuranylcarbonyl)propionic acid.

To a solution of 1.50 g. of the above compound in 25 ml. of ethanol isadded a solution of 0.8 g. of L-proline and 1.17 g. of sodiumbicarbonate in 25 ml. of water. The mixture is stirred at roomtemperature for 20 hours. The organic solvent is removed in vacuo andthe resulting aqueous slurry is diluted with 75 ml. of water, acidifiedto pH 2.5 with concentrated hydrochloric acid and extracted withdichloromethane. The organic layer is separated, dried over anhydroussodium sulfate and evaporated to give 1.0 g. of1-[3-(2-benzofuranylcarbonyl)propionyl]-L-proline as a glass.

To a solution of 0.76 g. of the preceding compound in 12 ml. of glacialacetic acid is added one drop of hydrogen bromide (48%), followed by thedropwise addition of a solution of 0.39 g. of bromine in 5 ml. ofglacial acetic acid over a 15 minute period. The mixture is stirred atroom temperature for 28 hours. The solvent is removed in vacuo and theresidue is chromatographed in a conventional manner using preparativethin layer chromatography, developing with ethylacetate:hexane (3:1)with 2% glacial acetic acid. The major band is collected and extractedwith tetrahydrofuran to give 0.34 g. of1-[3-bromo-3-(2-benzofuranylcarbonyl)propionyl]-L-proline.

The preceding compound (0.34 g.) is added to a stirred solution of 63mg. of potassium hydroxide and 85 mg. of thiolacetic acid in 2.0 ml. ofethanol. The mixture is stirred at room temperature for 3 hours, then isfiltered. The solid is washed with 2.0 ml. of ethanol. The combinedethanol filtrate and wash is evaporated in vacuo and the residue ispartitioned between dichloromethane and water. The organic layer iswashed with water, dried over anhydrous sodium sulfate and filtered. Thefiltrate is evaporated in vacuo to give 120 mg. of the product of theExample as a glass.

We claim:
 1. A compound selected from the group consisting of those ofthe formulae: ##STR21## wherein R₁ is hydrogen or alkyl having 1-3carbon atoms; R₂ is hydrogen or alkyl having 1-3 carbon atoms; R₃ ismercapto, formylthio, benzoylthio, alkanoylthio having 2-4 carbon atomsor moieties of the formulae: --S--CO₂ CH₂ C₆ H₅, --S--CO₂ R₅, --S--CH₂CO₂ R₅ or --S--CO-N(R₅)₂ ; R₄ is hydrogen or alkyl having 1-4 carbonatoms; R₅ is hydrogen or alkyl having 1-4 carbon atoms; and Heteroarylis selected from the group consisting of moieties of the formulae:##STR22## wherein R₆ is hydrogen, fluoro, chloro, bromo or alkyl having1-4 carbon atoms; and the pharmacologically acceptable cationic saltsthereof when R₅ is hydrogen.
 2. The compound according to claim 1,formula (III) thereof,1-[3-(acetylthio)-3-(2-thenoyl)propionyl]-L-proline.
 3. The compoundaccording to claim 1, formula (III) thereof,1-[3-acetylthio)-3-(5-bromo-2-thenoyl)propionyl]-L-proline.
 4. Thecompound according to claim 1, formula (III) thereof,1-[3-acetylthio)-3-(5-chloro-2-thenoyl)propionyl]-L-proline.
 5. Thecompound according to claim 1, formula (I) thereof,1-[2-(acetylthio)-3-(2-thenoyl)propionyl]-L-proline.
 6. The compoundaccording to claim 1, formula (III)1-[3-(acetylthio)-3-(2-thenoyl)-2-methylpropionyl]-L-proline.
 7. Thecompound according to claim 1, formula (II) thereof,1-[3-(acetylthio-4-(2-thenoyl)-2-methylbutyryl]-L-proline.